In existing communications models, the network centric approach is the dominant one. The network centric approach implies that services are provided by the network in a monolithic fashion, and he who owns the network owns the services. The implication is that the terminal or end user is restricted to the use of services offered by one or just a few operators. In addition these services are mainly offered on a subscription basis. The service offered to a user is typically a bundling of a set of supporting network services. The bundling is typically done in the switching systems (Local Exchanges, MSCs, etc.). There is little or no freedom to choose the best available service provider for these supporting network services on a call by call or session by session basis. For example, a phone service subscriber is more or less restricted to using the gatewaying services, transcoder services, and/or bridging devices for conferences provided by the phone service provider.
In a deregulated market, a multitude of service providers of all sorts of services are expected to be available on the market. This requires that the monolithic services of today be broken apart into their constituent parts and made available as separate services. Solutions to the basic problem of unbundling this services so that they may be easily accessible by anybody as well as provided by anybody have been proposed. For example, the publicly accessible stand alone gateway disclosed in European Patent Application Number 00850070.4, which is hereby incorporated herein by reference in its entirety.
A Gateway is a network node in a communications network, equipped for interfacing with another network that uses different protocols or different data formats. The gateways discussed herein interconnect higher layers than the link and network (IP) layer. The gateways support address mapping and can also provide transformation of the data between the networks to support end to end application connectivity such as conversion of file formats and the like. The networked support services provide by the gateways of interest are mainly those which actually process a media flow, and are typically: transcoder services (speech, audio, video); trans media services (e.g., text-to-speech); conference units and audio/video media mixers; security proxies (e.g., trusted security proxies for encryption/decryption); and other application layer gateways.
FIG. 1 shows a communications system 101 that utilizes a publicly accessible stand alone gateway as disclosed in European Patent Application Number 00850070.4. The communications system 101 includes a first entity A, for example a mobile terminal, and a second entity B, for example an end system or end user serving terminals involved in the same session. Two media components, C1 and C2, for example, voice and video, are to be transferred from the second entity b, over an IP network 102 to the first entity A, within the communications system 101. The A to B session invitation and negotiation 103 may be done, for example, using standard Session Initiation Protocol/Session Description Protocol (SIP/SDP) procedures. SIP is an application layer protocol for creating, modifying and terminating sessions with one or more participants. These sessions include Internet multimedia conferences, Internet telephony calls and multimedia distribution. SDP is a protocol intended for describing multimedia sessions for the purpose of session announcements, session invitation, negotiation and other forms of multimedia session control. In this example the second entity B can only support MPEG2 video C1, whereas entity A is a mobile terminal that has a small screen and can only handle H.261 video. Accordingly, a transcoding service is required that transcodes MPEG2 to H.261 video. The communications system 101 also includes a gateway system S offering the service of processing a media stream C1 which in the example implies transcoding of MPEG2 to H.261 video.
FIG. 2 shows a block diagram of a publicly accessible stand alone gateway which may be utilized by the invention. The gateway system 201 comprises a gateway controller 202 and a gateway 203 which are both connected to the IP network and each typically has an IP address. The gateway system 201 is available for external control through the gateway controller 202. The gateway controller 202 is publicly available via its published Universe Resource Identifier (URI) e.g., service@domain.
To access the Gateway and thus the services provided thereby, the first step is to configure the service. This is done with one or more service requests sent in a control protocol 206 from a first entity to the gateway controller. The control protocol may be based on SIP or SDP. It is also possible to send the service request in the same message exchange as the A to B session invitation. The gateway controller 202 is addressed using a URI in the form service@host (e.g., transcoder@services.operator.com) in the request. In the case where a SIP or SDP control protocol is employed, the URI would be used in the SIP Uniform Resource Locator (URL) according to known practice in the format sip:service@host. The service request typically contains information about type of service, e.g., transcoding from MPEP2 to H.261 and information about the address to which the stream should be sent, e.g., IP address and port number of first entity A and other necessary address information pertaining to the entities A and B and the associated media stream.
Accordingly, if for a specific call a user wishes to use a service provided by a gateway system, the gateway system is addressed for the purpose of configuration and activations, by means of the gateway's URI. This requires that the user know the URI of the gateway. The user configures the service for the specific call and activates the service.
However, a problem arises when the user is not within his home network, i.e., when the user is roaming. This results from the fact that the user typically, only knows the URI of the one or few gateways which provide a service in the users home network. Therefore, the user has a limited set of gateways to select from. This means that while roaming, there is no real means to select an “optimal” or preferred gateway, and problems such a tromboning the media stream to the “home” service provider's gateway while visiting another network occurs.
Therefore, a need exists for an automatic mechanism for providing a user with a preferred gateway on a call by call or session by session basis.